You may have a hard time filling a reservoir with a pen, since both essentially operate in a vacuum. You'd have better luck injecting from a pen into an empty (or near-empty) insulin vial, then pulling it into the reservoir that way. Be careful though, Apidra is very sensitive to the environment and has a short (2-day) shelf-life at room temperature.
Good luck with the CGM. I found it (and still find it) tough to get working at times, but when it works well, it's great.